Most existing power drills have a three jaw chuck for gripping a drill bit. The chuck jaws are adjustable to suit drill bits of various sizes. In most cases such adjustment is carried out by use of a key or by manually twisting the outer sleeve of the chuck or alternatively the user grips the outer sleeve and power is applied to the chuck, whereby the user provides a resistance force.
Other existing power drills, however, incorporate means for adjusting the chuck jaws which do not require a key or manually twisting the outer sleeve of the chuck or gripping the outer sleeve and applying power to the chuck, whereby the user provides a resistance force. One such existing power drill instead includes an adjustment mode and a drive mode. In the adjustment mode operation of a drive motor causes adjustment of the chuck and in the drive mode operation of the drive motor causes rotation of the chuck along with a working element gripped by the chuck for, say, drilling a hole into a workpiece.
Existing power drills that include an adjustment mode and a drive mode can include a mechanical assembly that is operable in providing the adjustment and drive modes and for switching between modes. However, in such power drills the mechanical assembly is typically located between the drive motor and the chuck and this can add considerably to the length of the power drill between the drive motor and the chuck and to the length of the power drill overall. This is a particular disadvantage when power tools incorporating a mechanical assembly such as the one described above are being marketing in competition with more compact power drills that do not incorporate such a mechanical assembly, such as power drills that do not include adjustment and drive modes.
In the field of power tools, in particular hand held power tools, it is desirable to be able to provide a power tool that is compact in order that the tool may be easily handled and be able to access confined spaces. Accordingly, whilst existing mechanical assemblies that provide adjustment and drive modes for a power tool may serve the purpose of providing adjustment and drive modes there is a need for a power tool, that provides adjustment and drive modes, and that is as short as possible.
Accordingly, it would be advantageous to be able to provide a mechanical assembly for a power tool that is operable for providing adjustment and drive modes for a driven member, such as a chuck, that is short in length. It would also be advantageous to be able to provide a mechanical assembly for incorporation in a power tool that is operable for providing adjustment and drive modes for a driven member and that provides a power tool that is compact.
Some existing power drills have a drive mode and an adjustment mode. When in the adjustment mode operation of a drive motor of the power tool causes the jaws of a chuck to move either towards or away from each other to either clamp or release a working element. When in the drive mode operation of the drive motor of the power tool causes rotation of the chuck along with a working element gripped by the chuck. Such power drills can include a torque control means for controlling the amount of torque applied by the drive motor to the chuck when the power drill is in the drive mode. However, the amount of torque that the torque control means allows to be applied may not be an appropriate amount of torque to prevent damage to the power tool or the working element when the power dill is in the adjustment mode for clamping or releasing a working element. In other words, the amount of torque required in the drive mode may be different to the amount of torque required in the adjustment mode. Thus, existing power tools incorporating adjustment and drive modes and a torque control means for controlling the amount of torque applied by the motor require a user to alter the torque control setting of the torque control means between when operating the power tool in the adjustment mode and when operating the power tool in the drive mode. In power tools in which the torque control means involves manually rotating a knob through a range of graduated torque settings or some other equivalent manual adjustment means, it is not convenient to have to adjust the torque control means whenever the user wishes to operate the power tool in the adjustment mode and the drive mode.
Accordingly, it would be advantageous to provide a power tool incorporating an adjustment mode and a drive mode and a torque control means which did not require the user to adjust the torque control means between when operating the power tool in the adjustment mode and the drive mode.